Process for the extraction of relatively pure vanadium, niobium and tantalum



Aug. 2, 1960 G. ERVIN, JR., ErAL 2,947,672

PROCESS FOR THE EXTRACTION 0F RELATIVELY PURE VANADIUM, NIOBIUM AND TANTALUM Filed Aug. 4, 1959 INVENTORS. Gu Y EEV/N J 2 'HEEBEET F6. E Z

A TTOENE Y United States Patent PROCESS FOR THE EXTRACTION. OF RELA- TIVELY PURE VANA'DIUM, NIOBIUM-:AND TANTALUM GuyfErvin, Jr.; EncinofCa'lifl, and Herbert F. G; Ueltz, I Shrewsbury, .Mass, assignors to iy-Norton-* Company,

Worcester, Mass.,-a-corporation= of Massachusetts Filed Aug 4; .1959, 'Ser'. No. 831,556

" 32 Claims (CI-z 204- 64) "The invention relates .to the extraction ,of relatively pure vanadium, niobium (olurhbiufn) and tantalum. This application is a continuation-in-part of our copending,applications Serial 1 #356,426 (vanadium), #356,4231 (.ni-

Patented Aug. 2, 1960 5 "'NaCl' -and'of course this'is the cheapest of all salts. In

" addition it" is easily obtained in an anhydrous condition "EJldlllS meltingpoint'is low enough in view of the fact ;'that we have found that'for the best results the tempera- ;1ture of the bath should be over 800 C. and we use an IOJeYerLhigher. temperature to avoidfreezing of the salt by 15. one is bbyiously'the ideal metal for the cathode.

obium), and #356,425 (tantalum), 'allfiled on May .21, 2

Q One object ofthe inventiondstoprovide a' thoroughly spractical and commercial. process. .for' the extraction ;'of uthese. metalswhich process can beoperat'ed.-at relatively ...low cost.

.of. the nature indicated utilizing asimpleapparatus which is ..quite. safe to operate. Another object of the invention gisato, provide a. process Jot the; nature 1 indicatedin which a single step. onlyis ,requiredvfor, transforiningjhe metal carbide, directly. into .these; metals, .in such, a. waylthat there .is no opportunity; foncontaminationby oxygen .or nitro- 1 vgen or--:other. ,undesriable gimpuritiesethat... are difficult. to :.remove. Another. object .of;.the invention isetqproduce a-these metals .in relatively :largegraintsize by means of. a =simpleaprocess. Another object is tomake malleableand ..-.=ductile metal. a

@Other objects iwillrqbe ,in.--part obvious .or; are inpart pointed outherein.

. 1 The .accompanying drawing is a. vertical aXialsectional view of electrolytic apparatus for carrying outtheprocess @of-the inventionafor. extraction of anyof thesemetals from 1 their carbides.

:We. have discovered a process. for.producingarelatively :pure metal;-.of.;the kinds indicated: the .basis. for which; is .1 :the electrolytic deposition-of metal "in "an, electrolytic. cell having a consumable anode made of carbide of the metal. The electrolytic bath is; composed :of :fusedwsaltwhich is shalide zofixmetal selected from the, groupvconsisting of the alkali metals and alkaline earth metals including :rz-nesium .and mixtures of such halides. -Also-we prefer :ctoxprovide a smallaarnountof .halide of themetal in quesztion. This accelerates "the process andhproduces purer :xmetlal. ;It makesulargerycrystals. We use the double :fiuorides when available, otherwisethe chlorides are the most practical .ofthehalideswhich are salts of the metal involved. Thus We prefer either-= VCl .,or.,K l-IbF or K Taf .The, melting points of the-chlorides of the alkali and alkaline earth metals are shown in the follow- "Barium chloride,'l3aCl 962 unavoidable variations in temperature. A preferred temperature, 900 C., is still low enough for an economical operation, alljthings considered.

'flFor' the extractionof any one of these metals the same But stainlessstjeel' is quite satisfactory also and chromium platedj stainless steel makes an excellent cathodefor ,the extraction of any of the three metals.

0 'jOne. ,appa.. .atus, and the best one now known to us,

F n Whichlthe, .processof this invention can be carried out fillustrated in thedrawing. -A refractory box 1 consist- '.--.ing...of a; sheetsteel cylinder 2,. to the bottom of which is ,welded abottom plate 3 andhaving a top plate 4 secured ...thereto :by bolts .5, is. filled with refractory brick. The

i .,ibo1c l isishown as supported by legs 3. Through a space Another object of the invention. is to provide. aprosless 7.10 in,.the,.brick extendresistor. bars 11 made of silicon .,carbide of a type. now well. known, these bars having socalled cold ends 12 as such bars practically always do. .Thecold-ends 12-extend through alumina sleeves 15 that extend throughthe top plate. 4 and the brick to receive mtlie upper cold ends 12 and through the brick and the bottom plate 3 to receive theplower cold ends 12. The lower'cold ends :lZ-are supported by refractory blocks 16 Which rest upon the lower horizontalportions of Z shaped irons l7 the upper horizontal portions ofwhich are welded to 'the -bottom-plate 3. Electricalconnections are made to the cold ends 12,-but these are well known and arenot shown. By, energizingithe barsll the temperature in the cell-20 can be brought to the desiredlevel.

The cell 20 is made of steel. i It has a hollow flange 21 through which cooling water is pumped by meansof connections. 2 2aand- 23. It is bolted by means of. bolts 212410 a head-plate 25 having a-hollow upward extension 26.:through which-water ispumped by means of connec- .tions 27and 28. Thehead plate 25 is sealed to the flange .21 by means of: a iringil, between theseparts. The ring 50 is made ofchlorinated butadiene.

The extensionrEfi has aflange' -whichis bolted-by means of bolts'36 to a flange 370m the bottomof a pipe shaped valve body 40 transversed by a vacuum seal valve apparatus ilWhlCl'l. canbe operated to seal off the space below it. This valve apparatus 4-1 is not shown in detail as it belongs in another art andpany goodgone can be i used.

Extending upwardlyfroni-the valve body "40 is a water 'cooled pipeSll. Thisiswprovided to allow the top of "the apparatus to become relatively cool. This pipe 50. has a bottom flangeSl and a top fiangeSZ, and from the bottom of the former tothe top of the latter the pipeis two feet high. The flange 51 is bolted to an upper flange SE-providedon the top of the valve bodyr itlby means *of-bolts 55. The flange 52 is, bolted to a plate 57 by means of bolts 58. The plate 57 has a central hole 60 and above this' central hole 60 is a rubbersealing tube olthe lower-part of which is reinforced with a steel sleeve 62. The rubber-sealing tube'ol is held down onto the plate5'7 by means of a-laminated cloth and phenolic resin-plate having ahole 66therethrough, hold down bolts 67 extending-between the iplate'157.;and the-plate 65 being provided to hold' theseiplatesztogether. The water cooled pipe 50 is cooled-by a waterchamdesirable for about twenty-four hours.

' rupted for short periods).

her 70 welded thereto and connections 71 and 72 to circulate the water. A gasket 73 is provided between the flanges 57 and 53 and a sealing ring 74 is provided between the flanges 57 and 52, both of these being made atmosphere which may be generated during the elecv 80 exhausting the gas through a lower pipe 81, the former for example extending into the top of the pipe 50 and the latter into the flange 25 and connected to a bore 82 extending to the inside of the extension 26. We find it is preferable'to have the argon entrance above the argon exit to drive salt vapor downwardly to keep it from plugging the upper part of the apparatus. The, system should be flushed with argon before starting electrolysis Argon is pumped all of the time during electrolysis (but could be inter- In an apparatus of this size a flow of argon of two cubic feet per hour is satisfactory.

The steel cell 20 (an ordinary low carbon steel was used) was 5% inches inside diameter. The extension 26,

.rnade of the same steel, had an inside diameter of 3% inches and so did the valve body 40 and the pipe 50. All of these parts were made of the same steel except the body 40 which was made of aluminum. Dimensions of the apparatus not mentioned can be calculated closely by sealing the drawing relative to a dimension given.

The cell 20 was Nichrome plated on the outside, by flame spraying.

Fitted into the cell 20 is a graphite crucible 90 and the drawing sufliciently shows its shape and position. Inside of the graphite crucible 90 is a long sleeve made up of a series of anode rings 100 of metal carbide bonded with pitch in the manner to be particularly described.

A long rod shaped cathode 101 extends in an axial position relative to the cell 20 the crucible 90 and the sleeve 100, vertically from close to the bottom of the anode 100 through the extension 26, through the valve body 40, through the valve mechanism 41 when the valve thereof is open, through the pipe 50, through the hole 60, through the rubber sealing tube 61 and through the hole 66, projecting a slight distance above the plate 65. i There it is connected by a clamp to the negative side of a source of direct current electrical energy as indicated by the negative sign above its top. The cell 20 and therefore also, through the crucible 90, the anode 100 is connected by electrical connections to the other side of the circuit which is therefore a source of positive electricity as indicated by a positive sign close to the bottom of the bolt 24 that is shown, a convenient place to make the connection. But any way of connecting the anode 100 to the positive side of the source is upwardly through the sealing tube 61 until its bottom has cleared the valve mechanism 41. Then the valve is closed. After an interval of time usually about an hour to allow the cathode 101 where the metal has collected thereon and said metal to cool down enough to avoid reaction with the air, the plate 65 is unbolted and lifted up and off the cathode 101, and then the cathode 101 with the deposit of metal is entirely removed from the system, and the metal is scraped off and collected for further processing which need not be described herein. Briefly such processing involves dissolving off the salt clinging to the-metal, pressing the sponge metal so clean of salt, melting it in a vacuum and casting ingots, or, instead of melting and casting the metal, it can be pressed and sintered to form articles.

While the bottom of the cathode 101 and the metal thereon is cooling in the valve body 40 and pipe 50, argon 4 or other inert gas is pumped from the pipe 80 to an exhaust pipe 105 having a valve 106 so that it can be opened at this time and closed when the cathode 101 is down and the process is operating.

Example l.-Vanadium Ten pounds of vanadium carbide, VC, are pulverized by' ball milling dry in a steel ball mill sothat the material will pass through a 100 mesh screen (Tyler series). The pulverized VC is acid washed by placing it in a 40 gallon stoneware crock. Ten liters of a solution of 5% by volume of commercial concentrated H 80 and 95% by volume of distilled water is placed in the crock with the VC. A copper steam coil and an agitator with a rubber propeller are placed in the mixture. and steam at about 10 pounds pressure is-turned on and passed through the coil to heat the mixture. After the reaction has subsided or in about 10 hours the coil is removed and the V0 is allowed to settle. The supernatant liquor is eliminated after 24 hours by siphoning and distilled water is added. The mixture is rinsed in this manner 6 times. The final rinse water is siphoned off and the sludge is dried in an enameled basin in an air circulating oven at 200 F.

A mixture consisting of 10% by weight hard pitch a and 90% by weight VC powder is made by blending 360 grams of pulverized hard pitch (200 mesh, M1. 285 to 315 F.) with 3240 grams of acid treated and dried VC powder in a sealed fiber carton and rolling on a roller mill for two hours. Six rings, 4%, OD. x 3% ID. x 2" high are pressed from the mixture by conventional cold pressing techniques in a steel mold at 3 tons per square inch. Each ring weighs approximately 600 grams and the density is approximately 3.54 g./cc.

The six rings are stacked in the graphite crucible and placed in the cell 20. The cell is placed in the furnace. Argon gas is fed in the gas inlet. The pitch volatiles are baked out and are carried out the gas outlet by argon gas and trapped in a steel condenser. The temperature is raised in 200 C. increments to 1000 C. in 5 hours and the rings are baked at 1000 C. for five hours. After cooling, the head 26 is removed and pitch volatile greasy condensate is scraped from the cool surfaces inside the cell, which-are then cleaned with solvent such as acetone.

The pitch loses 52% by weight due to baking out the volatiles and leaves 48% carbon as the bond. The weight of the six rings after baking is approximately 3400 grams. The height of the lining is 12. inches. The density of the carbon bonded V0 is approximately 3.37 g./cc. The volume of the pores is approximately 36% The capacity of the lined crucible is 2.2 liters. Approximately 2600 grams of vanadium are available for electrolytic extraction. 7

The cavity of the crucible is filled with 3860 grams ofelectrolyte. The electrolyte is made up of 3582 grams of C.P. sodium chloride and 2.78 grams of vacuum dried VCl Because of the deliquescent characteristic of VCI care has to be taken to keep exposure to air at a minimum. This quantity of electrolyte will give a molten salt bath depth of about 12 inches at operating temperature, with a soluble vanadium concentration of 3%.

flowing through the cooling chambers. The vacuum pump and a Dry Ice trap are connected and the system is evacuated. The electrolyte and interior surfaces of a The temperature is turned to C. without water nhances *ininute. When the leakrat is lielow 200 micron liters =dium cathode is lowered into the electrolyte, while im- 1 pressing a small voltage upon it, until the lower end of thecathode is two'inches above the bottom of the crucible.

The DC. rectifier is turned to 200 amperes, a voltage in the range of from about 5 to volts being'required.

After-"'tme' hour, the direct current is shut olf andthe cathode and deposit are withdrawn into cooling chamber 40. Valve 41 is closed, the cathode with adhering deposit is allowed to cool and then is removed from the chamber 40.

The deposit with 'entrappedsalt ischipped from the cathode and crushedand leached with-distilled water until -alltraces ofelectrolyte'are gone. The metal powder is compac'tdby pressing in a steel mold and melted into avanadium metalingot in an' atmosphere of pure argon in a Water-cooled arc furnace.

Example II.'-Ni 0bium In a manner similar to that of Example I, pounds 0f niobium carbide, NbC, are prepared. A 7.6 percent by weight mixture of pitch .and' 92.4. percent by weight prepared NbC powder is made by blending 4400 grams of NbC and 360. grams of hard pitch. Six rings each weighing 794 grams and measuring 4 OD. x 3%" ID. x 2 high are pressed from the mixture at three tons per square inch. Their density is approximately 4.68 g./cc. The rings are baked as described in Example I. The density of the baked carbon bonded lining is about 4.50 g./cc. and the volume of pores is approximately 36%. Approximately 3900 grams of niobium are available for electrolytic extraction.

The electrolyte is made up of 3480 grams of CF. sodium chloride and 380 grams of vacuum dried K NbF This is blended and placed in the cell in a manner similar to that described in Example I. The electrolyte is vacuum dried as in Example I and the electrolysis is similarly made using a niobium cathode. The deposit is removed and treated as in Example I to produce a niobium metal ingot.

Example [IL-Tantalum In a manner similar to that of Example l, 25 pounds of tantalum carbide, TaC, is prepared. A 4.2 percent by weight mixture of pitch and prepared Ta-C powder is made by blending 8220 grams of TaC and 360 grams of hard pitch. Six rings each of 1430 grams weight and 4% O.D. X 3%" ID. x 2" high in dimensions. are pressed from the mixture at three tons per square inch. Their density is approximately 8.42 g./cc. The rings are baked as described in Example I. The density or" the baked carbon bonded lining is about 8.25 g./cc. and the volume of pores is about 36%. Approximately 7700 grams of tantalum is available for electrolytic extraction.

The electrolyte is made up of 3609 grams of GP. sodium chloride and 251 grams of vacuum dried KzTZlF This is blended and placed in the cell in a manner similar to that described in Example I. In a manner similar to Example I, the electrolyte is vacuum dried and the electrolysis is made using a tantalum cathode. The deposit is removed and treated as in Example I to produce a tantalum metal ingot.

Vanadium, niobium formerly called columbium in America although it has been called niobium in Europe for a good many years, and tantalum are generally similar in chemical characteristics. Each one is a refractory metal of the fifth group of the periodic table. Since in this process their carbides act the same, they are properly grouped together herein. A mixture of vanadium carbide and niobium carbide, a mixture of niobium carbide and tantalum carbide, or a mixture of vanadium carbide and tantalum carbide could be used in this process to obtain r:ani:alloy. of.vanadium andniobium or niobium and tantalum or vanadium and tantalum, or amixture of all three carbides could be. used to obtain an alloy of vanadium,

niobium and tantalum. Someday itwill probably be de sirable to produce relatively pure alloys of the above nature and ouruprocess lends itself excellently to such z'production. Almost aniinfinite number of alloys can be produced according to. the present process.

f There are three best modes of the invention described herein. We havedescribed the best mode for vanadium x in Example I, and the best mode for niobium in Example II, and for tantalum in'ExampleIlI. Further than that we cannot go. The apparatus described is the best new known to us and the principal way'to. improve it is to make it bigger.

It will thus be seen that there has been provided by this .Winvention a process for the extraction of relatively pure vanadium, niobium, and tantalum in which the various *objectslhereinabove: set forth together with many thoroughly practical advantages are successfully achieved. As

ntmanypossible embodiments-may be made of the above invention and as many changes might be made in the vembodiments above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be" interpreted as illustrative and xIthe'fifth group-consisting of vanadium, niobium and tantalum and mixtures thereof which 'comprises"passing a direct electric current through a cell having a solid anode and a solid cathode in a direct current electric circuit, the electrolyte in said cell consisting, apart from any fifth group metal halide content, essentially of fused halide of metal selected from the group consisting of alkali metals and alkaline earth metals including magnesium and mixtures of such halides, said cell containing fifth group metal carbide in said halide electrically connected to the positive side of the electric circuit and collecting the fifth group metal electrolytically liberated at the cell cathode.

2. Process for the preparation of vanadium which comprises passing a direct electric current through a cell having a solid anode and a solid cathode in a direct current electric circuit, the electrolyte in said cell consisting, apart from any vanadium halide content, essentially of fused halide of metal selected from the group consisting of alkali metals and alkaline earth metals including magnesium and mixtures of such halides, and said cell containing vanadium carbide in said halide electrically connected to the positive side of the electric circuit and collecting the vanadium metal electrolytically liberated at the cell cathode.

3. Process for the preparation of niobium which comprises passing a direct electric current through a cell having a solid anode and a solid cathode in a direct current electric circuit, the electrolyte in said cell consisting, apart from any niobium halide content, essentially of fused halide of metal selected from the group consisting of alkali metals and alkaline earth metals including magnesium and mixtures of such halides, said cell containing niobium carbide in said halide electrically connected to the positive side of the electric circuit and collecting the niobium metal electrolytically liberated at the cell cathode.

4. Process for the preparation of tantalum which comprises passing a direct electric current through a cell having a solid anode and a solid cathode in a direct current electric circuit, the electrolyte in said cell consisting, apart from any tantalum halide content, essentially of fused halide of metal selected from the group consisting of alkali metals and alkaline earth metals including magnesium and mixtures of such halides, said cell containing tantalum carbide in said halide electrically connected to the positive side of the electric circuit and collecting the tantalum metal electrolytically liberated at the cell cathode.

' made of said carbide.

6. Process according to claim in which the portion of the fused halide is chloride.

7. Process according to claim 6 in which the portion of the fused halide is alkali metal halide.

8. Process according to claim 1 in which the portion of the fused halide is chloride.

9. Process according to claim 8 in which the portion of the fused halide is alkali metal halide.

10. Process according to claim 1 in which the major major major major major portion of the fused halide is alkali metal halide.

11. Process according to claim 10 in which the is made of said carbide.

12. Process according to claim 2 in which the is made of said carbide.

13. Process according to claim 12 in which the portion of the fused halide is chloride.

14. Process according to claim 13 in which the portion of the fused halide is alkali metalhalide.

15. Process according to claim 2 in which the portion of the fused halide is chloride.

16. Process according to claim 15 in which the portion of the fused halide is alkali metal halide.

17. Process according to claim 2 in which the portion of the fused halide is alkali metal halide.

18. Process according to claim 17 in which the is made of said carbide.

19. Process according to claim 3 in which the is made of said carbide.

anode anode.

anode '20. Process according to claim'19 in which the major portion of the fused halide is chloride.

21. Process according to claim 20 in which the major port-ion of the fused halide is alkali metal halide.

22. Process according to claim 3 in which the major portion of the fused halide is chloride.

23. Process according to claim 22 in which the major portion of the fused halide is alkali metal halide.

24. Process according to claim 3 in which the major portion of the fused halide is alkali metal halide.

25. Process according to claim 24 in which the anode is made of said carbide.

26. Process according to claim 4 in which the anode is made of said carbide.

27. Process according to claim 26 in which the major portion of the fused halide is chloride.

28. Process according to claim 27 which the major portion of the fused halide is alkali metalhalide.

29. Process according to claim 4 in which the major portion of the fused halide is chloride.

30. Process according to claim 29 in which the major portion of the fused halide' is alkali metal halide.

31. Process according toclaim 4 in which the major portion of the fused halide is alkali metal halide.

32. Process according to claim 31 in which the anode is made of said carbide.

No references cited. 

1. PROCESS FOR THE PREPARATION OF METAL SELECTED FROM THE FIFTH GROUP CONSISTING OF VANADIU, NIOBIUM AND TANTALUM AND MIXTURES THEREOF WHICH COMPRISES PASSING A DIRECT ELECTRIC CURRENT THROUGH A CELL HAVING A SOLID ANODE AND A SOLID CATHODE INA DIRECT CURRENT ELECTRIC CIRCUIT, THE ELECTROLYTE IN SAID CELL CONSISTING, APART FROM ANY FIFTY GROUP METAL HALIDE CONTENT, ESSENTIALLY OF FUSED HALIDE OF METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS INCLUDING MANGESIUM AND MIXTURES OF SUCH HALIDES, SAID CELL CONTAINING FIFTH GROUP METAL CARBIDE IN SAID HALIDE ELECTRICALLY CONNECTED TO THE POSITIVE SIDE OF THE ELECTRIC CIRCUIT AND COLLECTING TO THE GROUP METAL ELECTROLYTICALLY LIBERATED AT THE CELL CATHODE. 